1. Field of the Invention
This invention relates generally to data processing systems and more particularly to apparatus for measuring activity required by a central processing unit of a data processing system for execution of a program.
2. Description of the Related Art
In the related art, it is known to measure the usage of a data processing system by measuring (at least in part) the time required by the central processing unit for the execution of a program. A numeric value can be loaded into an arithmetic circuit at the beginning of a program and the value in the arithmetic circuit decremented in response to periodic clock signals generated by the data processing system. When the arithmetic circuit reaches zero, control of the program would be returned to a supervisor program. The supervisor program would then determine whether to continue the program currently in execution or to intitiate some other activity in the data processing unit.
It has been found that measuring the activity of a central processing unit resulting from the execution of a program can vary from system to system because of the characteristics of the different data processing systems. As a result, when a multiprocessor system is being utilized as a data processing utility, this measurement can result in different customer charges for execution of the same program, the difference depending on the particular central processing unit. Furthermore, system activity can affect the availability of data processing resources with the result that a different activity period can be measured for the same program execution in the same data processing system. A need therefore existed for more accurate measurement of the activity of the central processing unit of the data processing system, obtained by measurements that were not directly based on a continuously running clock, but were based on other parameters, parameters related to the activity of the central processing unit required for execution of the program.